Mr Conroy said that despite reports that many people have fled Homs, there are still thousands of people there, living in "bombed out wrecks" and "waiting to die".

He said: "It's more than a catastrophe. It's snowing there now, people can't light fires.

"It's complete failure. In years to come, we're going to sit and we're going to go 'how did we let this happen under our nose?"'

When asked what he thought the people of Homs and Syria would want him to say on their behalf, Mr Conroy added: "I would say 'somebody please forget the geo-politics, forget the meetings, forget all of that, do something', because as I'm talking to you now they're dying.

"They would say please send help. They need help. This is beyond meetings."

On leaving the body of Ms Colvin behind, Mr Conroy said: "Sadly it was one of the hardest decisions I've ever had to make."

He said Ms Colvin "would have wanted the story (told) over anything", adding: "Dear friends, the world has lost one of its greatest observers and it'll be a worse place without her."

Mr Conroy added that he hopes Ms Colvin's death is honoured by doing something to help the people of Syria.